SOLVOLYSIS OF ARYLCYCLOHEXYL CHLORIDES IN METHANOL ACETONITRILE MIXTURES/

Citation
Hk. Oh et al., SOLVOLYSIS OF ARYLCYCLOHEXYL CHLORIDES IN METHANOL ACETONITRILE MIXTURES/, New journal of chemistry, 21(11), 1997, pp. 1197-1202
Citations number
30
Categorie Soggetti
Chemistry
Journal title
ISSN journal
11440546
Volume
21
Issue
11
Year of publication
1997
Pages
1197 - 1202
Database
ISI
SICI code
1144-0546(1997)21:11<1197:SOACIM>2.0.ZU;2-G
Abstract
Solvolysis of 1-(X-phenyl)-1-cyclohexyl chlorides in methanol/acetonit rile mixtures was studied at 30.0 and 40.0 degrees C. The rho(x)(+) va lues, -4.67 to -4.81 at 30.0 OC, are within the range of rho(x)(+) for the solvolysis of secondary and tertiary compounds, which are believe d to react by an S(N)1 mechanism. Relatively large slopes (m greater t han or equal to 1.0) of the Grunwald-Winstein mY(1-AdOTS) plots sugges t that the positive charge developed in the transition state is consid erable and is delocalized onto the aromatic ring. The cross-interactio n constant Theta (= partial derivative m/partial derivative sigma(X) = partial derivative rho(X)(+) Y) is positive and nonnegligible (+0.54) , which indicates that the solvent effect on the localized charge (par tial derivative Y>0) is the opposite of that on the delocalized positi ve charge (delta rho(X)(+)>0 or delta(-rho(X)(+))<0). Solvent isotope effects (k(H)/k(D) = 1.12-1.17 at 40.0 degrees C), weak common-ion mas s-law effects, and the range of activation parameters (Delta H-not equ al = 18-22 kcal mol(-1) and Delta S-not equal = -1 to -15 cat mol(-1) K-1) are all consistent with the proposed S(N)1 mechanism.